1. Field of the Invention
This invention relates to a door lock assembly, more particularly to a door lock assembly having a retaining plate to removably hold a handle on a spindle tube.
2. Description of the Related Art
It is known to provide a door lock with a handle that carries a key-operated lock and that is connected to a spindle tube through which a latching device can be operated to latch or unlatch a door. Typically, the handle is connected removably to the spindle tube through a retaining plate that is disposed within the spindle tube and that is biased by a spring to interlock with a retention slot provided in the handle. The handle has a tubular body connected to the spindle tube and a longitudinal slot receiving a key-operated cylinder lock having a key plug connected to a tailpiece to operate the latching device. The retaining plate is disposed transversely in the longitudinal slot and is biased to project into the retention slot in the tubular body of the handle, thereby holding the handle on the spindle tube. When it is necessary to detach the handle from the spindle tube, the cylinder lock is first placed in an unlocking position, and a tool such as a pin is inserted into a tool hole formed in the tubular body of the handle to press the retaining plate so that the retaining plate is moved away from the retention slot and the handle can be removed from the spindle tube to replace the key-operated lock for re-keying.
Therefore, in order to prevent removal of the handle from the spindle tube against burglary, it is important that the retaining plate must be retained in the retention slot. In the conventional door lock, while the retaining plate can be kept in the retention slot through abutment with the tailpiece of the key-operated lock which is rotated to a locking position, due to the clearances that are likely to occur at the connection between the key plug and the tailpiece, the tailpiece can be swung to and fro by an external force and thus will be insufficient to rigidly support the retaining plate. Therefore, there is a likelihood incidence that the retaining plate may be removed undesirably from the retention slot by an external force when the key-operated lock is in the locking position.
U.S. Pat. No. 5,077,994 discloses a door lock having a lever handle that is removable from a rotary spindle for re-keying. The door lock includes a retaining plate 40 disposed transversely in a tubular body of a lever handle and is biased by a resilient block 70 that is disposed in a slot of the tubular body. The retaining plate has an aperture 48 and a downward lobe 50 projecting into the aperture. A lock tailpiece is connected to a plug 64 which is formed with a longitudinal groove 66 and which extends through the aperture. To rekey the door lock, the plug is rotated by a key to an angle (see FIG. 3) so that the groove on the plug receives the lobe on the retaining plate when the retaining plate is pressed by a tool inserted into a retention slot in the tubular body. In FIG. 2 of the patent, the lock tailpiece is in a locking state, and the retaining plate extends into the retention slot. Because the groove on the plug moves away from the lobe, and because the lobe can abut against the periphery of the plug when the retaining plate is pressed, the lever handle is prevented from being detached from the spindle tube against burglary when the door lock is in the locking position.